(1 of )Water from the Eel River collects at the Van Arsdale Reservoir and flows over the Cape Horn Dam. A percentage of the water is redirected through a diversion tunnel, at the building in the background, to the Potter Valley Powerhouse and east fork of the Russian River.
(Christopher Chung/ The Press Democrat)

(2 of )Water diverted from the Eel River turns generators inside PG&E's Potter Valley Powerhouse hydroelectric plant, which releases the water into the East Fork of the Russian River in Mendocino County on Thursday, April 6, 2017.
(Christopher Chung/ The Press Democrat)

(3 of )Water diverted from the Eel River flows out of the Potter Valley Powerhouse into the east fork of the Russian River in Potter Valley on Thursday, April 6, 2017.
(Christopher Chung/ The Press Democrat)

(4 of )Potter Valley Powerhouse, map

(5 of )The West Canal carries water past a ranch along Main Street, near Hawn Creek road, in Potter Valley on Thursday, April 6, 2017.
(Christopher Chung/ The Press Democrat)

(6 of )Water travels past a vineyard along the East Canal downstream from the Potter Valley Powerhouse, in Potter Valley on Thursday, April 6, 2017.
(Christopher Chung/ The Press Democrat)

(7 of )Janet Pauli inspects the East Main Canal in Potter Valley, water diverted from the Eel River and used to irrigate vineyards, orchards and pastures in the 7,000-acre valley. The canal runs along the edge of a Pauli merlot and pinot noir vineyard, Wednesday April 6, 2016. (Kent Porter / Press Democrat) 2016

(8 of )A large pipe carries water from the Van Arsdale Reservoir, fed by the Eel River, to the Potter Valley Powerhouse, in Potter Valley on Thursday, April 6, 2017.
(Christopher Chung/ The Press Democrat)

(9 of )Eel River above Lake Pillsbury, a reservoir in Lake County that is part of PG&E's Potter Valley Project.. (PG&E)

(10 of )Eel River above Lake Pillsbury, a reservoir in Lake County that is part of PG&E's Potter Valley Project. (PG&E)

(11 of )Eel River below Cape Horn Dam, which is part of PG&E's Potter Valley Project. (PG&E)

(12 of )Eel River below Lake Pillsbury, a reservoir in Lake County that is part of the Potter Valley Project. (PG&E)

(13 of )Eel River above Outlet Creek in Mendocino County. (PG&E)

(14 of )Lake Pillsbury, a reservoir on the Eel River in Lake County that is part of PG&E's Potter Valley Project. (PG&E)

(15 of )Scott Dam on the Eel River impounds Lake Pillsbury, a reservoir in Lake County that is part of PG&E's Potter Valley Project. (PG&E)

(16 of )The Eel River pours from Van Arsdale Reservoir over the top of Cape Horn Dam in Mendocino County, part of PG&E's Potter Valley Project. (PG&E)

(17 of )A water intake structure at Van Arsdale Reservoir in Mendocino County pulls water from the Eel River as part of PG&E's Potter Valley Project. (PG&E)

(18 of )A penstock carries water from the Eel River to a PG&E powerhouse in Potter Valley. (PG&E)

(19 of )A penstock carries water from the Eel River to a PG&E powerhouse in Potter Valley. (PG&E)

(20 of )PG&E's Potter Valley Powerhouse generates electricity with water drawn from the Eel River in Mendocino County. (PG&E)

(21 of )Water drawn from the Eel River spills from a tailrace behind PG&E's Potter Valley Powerhouse and becomes the start of the East Fork of the Russian River. (PG&E)

(22 of )A historic photo shows Cape Horn Dam on the Eel River in Mendocino County, part of PG&E's Potter Valley Project. (PG&E)

(23 of )A historic photo shows Cape Horn Dam on the Eel River in Mendocino County, part of PG&E's Potter Valley Project. (PG&E)

(24 of )A historic photo shows a penstock under construction, designed to carry Eel River water to a powerhouse in Potter Valley. (PG&E)

(25 of )A historic photo shows a team of horses hauling a generator to a powerhouse in Potter Valley. (PG&E)

(26 of )A historic photo shows the Potter Valley Powerhouse about 1910, just after it was built to generate electricity using water diverted from the Eel River. (PG&E)

(27 of )A historic photo shows Scott Dam under construction on the Eel River, looking upstream at the area to be inundated by Lake Pillsbury in Lake County. (PG&E)

(28 of )Scott Dam. (PG&E)

(29 of )Scott Dam without gates. (PG&E)

(30 of )Cape Horn Dam Fish Ladder - Original. (PG&E)

(31 of )Cape Horn Dam Fish Ladder – Current. (PG&E)

(32 of )Van Arsdale Fisheries Station. (PG&E)

(35 of )Water from the Eel River collects at Van Arsdale Reservoir and flows over Cape Horn Dam. A percentage of the water is redirected through a diversion tunnel to the Potter Valley Powerhouse and into the east fork of the Russian River. (CHRISTOPHER CHUNG / The Press Democrat)

(36 of )(File photo) Water from the Eel River collects at the Van Arsdale Reservoir and flows April 6, 2017 over the Cape Horn Dam. A percentage of the water is redirected through a diversion tunnel, at the building in the background, to the Potter Valley Powerhouse and east fork of the Russian River. (Christopher Chung/ The Press Democrat)

Fate of flows in Russian and Eel rivers rests in big fight over small hydroelectric project

Even the record rainfall that dowsed the North Coast this winter, filling reservoirs and streams, will not be enough to head off a looming clash over the water that courses down two of the region’s largest rivers, the Russian and the Eel.

Together, they drain a swath of territory, including cities, forests and vineyards, that stretches from central Sonoma County to Fortuna, in Humboldt County — an area larger than Connecticut.

A key link between the two rivers, a small powerhouse more than 100 years old, is now the focal point in a fight over the water that flows down these rivers. It’s a standoff with many of the main players in western water wars — farmers, environmentalists, water districts serving urban customers and fishermen. And it raises many of the same questions: Who benefits and who loses from water taken for decades from one river — at over 20 billion gallons a year — and funneled into another river?

In this case, it is the Eel River that has been tapped, its water sent down a milelong tunnel through a mountain in Mendocino County, into a PG&E powerhouse and ultimately into a fork of Russian River, which flows down through Sonoma County.

Water drawn from the Eel River sustains Lake Mendocino, the main source of drinking water for residents along the Russian River from Redwood Valley down to Healdsburg.

Turning off that supply could devastate agriculture and diminish that primary water source for thousands of people, according to interests on one side of the tug-of-war.

The vast majority of the more 600,000 North Bay residents who depend on the Russian River for drinking water are unaware of the plumbing arrangement and the controversy that has long swirled around it and two related dams on the Eel River, where once-prolific runs of salmon and steelhead trout have dwindled amid various human impacts, water diversion among them.

But for the partisans — the water managers, environmentalists, public officials, ranchers and scientists — the dilemma of parsing out this water between competing interests, between people and fish, between town and country, is revving up again over the relicensing of the PG&E powerhouse, called the Pottery Valley Project.

“It’s a critical moment,” said Rep. Jared Huffman, the San Rafael Democrat whose North Coast district spans the adjacent watersheds.

While Huffman hopes to carve out a consensus, there’s little common ground between environmentalists who want to stop the inter-county transfer of Eel River water, which some consider an out-and-out grab, and those who use that water to support agriculture worth hundreds of millions of dollars along the Russian River in Mendocino and Sonoma counties.

“Water is wealth,” said David Keller of Petaluma, a leader of Friends of the Eel, a group that has tried for more than two decades to halt the water diversion for the sake of salmon and steelhead driven toward extinction in the damaged Eel River watershed.

Janet Pauli, a longtime Potter Valley rancher and irrigation district official, adamantly defended the way water has flowed since the early 1900s.

“An economy, a way of life, a quality of life, has evolved with the existence of that water,” she said.

“Your classic water war,” said Josh Fuller, a biologist with the National Marine Fisheries Service, which will serve, in effect, as a referee in the dispute.

It will take at least five years and most likely longer for the federal agency to make a decision, and although PG&E’s 496-page filing doesn’t mention it, decommissioning the project — including removal of the only two dams on the Eel River, ending the water diversion and shuttering the powerhouse — will be on the table.

“There is bound to be controversy,” Fuller said, adding that decommissioning will be part of his agency’s assessment of the hydropower project’s future.

But Fuller was careful not to pass judgment on decommissioning at this stage, saying his agency “must stay scientifically objective, asking and investigating the right questions.”

David Moller, a director in PG&E’s power generation department, said decommissioning is “a possibility to be looked at” in any relicensing case.

“It may well be some participants have an interest in decommissioning,” he said. “Anything about relicensing is hard to predict.”

Huffman said he is focused on the relicensing process, not on any specific outcome.

“Nobody’s going to get everything they want,” he said. “There is risk on all sides. That is a situation that should bring everyone to the table.”

But the congressman said that Mendocino and Sonoma counties should “start preparing strategies” for loss of the diverted water, while those hoping to see a free-flowing Eel River should consider that a move to pull out dams would likely trigger a prolonged political and legal fight.

Early 20th-century link

The plumbing connection between the two rivers was made possible by a geographical fluke. Both arise not far apart from headwaters in the Mendocino County highlands.

The Eel’s 200-mile main stem courses north into Humboldt County, flowing mostly through forest lands and reaching the ocean near Fortuna. The Russian swings south, flowing 110 miles through Mendocino and Sonoma counties, with cities, ranches, parks and highways along the way to the coast at Jenner.

But at a point just north of Potter Valley, the upper Eel River comes within two miles of the headwaters of the Russian River’s East Fork, separated by a narrow ridge and 475 feet below the Eel.

A San Francisco industrialist, W.W. Van Arsdale, capitalized on the topography, drilling a mile-long tunnel and a constructing a series of pipes to carry Eel water to a small powerhouse in Potter Valley, which began operating in 1908.

A 63-foot barrier, Cape Horn Dam, initially backed up water for the diversion, and a larger one, 130-foot Scott Dam, was added in 1922, forming the Lake Pillsbury reservoir that provides water for year-round power generation.

The two dams, tunnel and powerhouse form the Potter Valley Project, granted a 50-year federal license in 1922. It expired in 1972, and it took until 1983 to relicense it for another half-century, through 2022. FERC requires relicensing to start five years before the expiration date, hence the start this month.

Potter Valley was a power project, developed by Ukiah to replace the city’s coal-fired plant. It generates enough electricity for about 7,000 homes. Water pouring from the plant’s tailraces was a side benefit, and valley ranchers formed an irrigation district, building a network of canals to move it around the 7,000-acre valley starting in 1928.

The result transformed an arid part of Mendocino County, limited to dry-farming cattle and hay, into an agricultural powerhouse that produces $34 million worth of wine grapes, pears, grass-fed cattle and other products a year. The imported water keeps the valley green as the surrounding hills turn gold, an Eden visible from airliners passing 36,000 feet overhead.

But the diversion is more than a bonanza for a little valley with 380 water customers.

The diverted water not used in Potter Valley — ranchers have rights to a little over a quarter of the supply drawn out of the Eel — goes into the East Fork of the Russian River, flowing into nearby Lake Mendocino, where it becomes part of the regional water system run by the Sonoma County Water Agency.

A report commissioned by Mendocino County groups estimated the economic impact of agriculture from Redwood Valley to the Sonoma County line at $743 million along with 5,000 jobs.

The Russian River watershed is “the economic engine for the county of Mendocino,” Brown said.

Decommissioning the project would have a “devastating effect” throughout the watershed, she said.

The Sonoma County Farm Bureau, recognizing the long reach of water from Lake Mendocino, supports relicensing the Potter Valley Project, said Tito Sasaki, chairman of the bureau’s water committee.

If that water were cut off, most of the grape growers in the famed Alexander Valley viticultural area would be hard-pressed to irrigate their vineyards, he said. Water rights mean nothing if the river flow falls below the minimum required for salmon and steelhead, he said.

Even well water could be restricted, Sasaki said.

Lake Mendocino is the sole source of water to maintain summertime stream flows in the river above Dry Creek, which brings in water from Lake Sonoma, the region’s largest reservoir. And residents north of Windsor depend on the river for drinking water, said Grant Davis, general manager of the Sonoma County Water Agency.

Davis said he “can’t even fathom” what decommissioning would do to the fish in the upper river — and it would be hard on people, as well.

What many people do not realize, he said, is that Lake Pillsbury, the cornerstone of Potter Valley Project, is the source for most of shallow Lake Mendocino’s water throughout the dry season.

Without inflow from the Potter Valley Project, Lake Mendocino would go dry in 60 percent of the years from 2015 to 2045, a Water Agency study found.

In such years, any private well tied to the river would be in danger of going dry, too, officials said.

Struggling fish species

Diversions from the Eel River currently total 70,000-acre-feet a year, following a cutback from 160,000-acre-feet in 2006. That amount exceeds deliveries by the Water Agency to its Sonoma and Marin customers, averaging about 50,000-acre-feet over the past five years.

Over the years, the supplemental supply from the Eel and the dams in place to support it have had drastic impacts on the river’s salmon and steelhead, environmentalists and fishermen say.

Keller, the Eel River advocate, and his allies continue to press for removal of the Eel River dams, allowing salmon and steelhead to migrate into the river’s upper reaches, cut off since Scott Dam was installed nearly a century ago.

Decommissioning would also end the water diversion, which claims 75 to 90 percent of the flows released from Lake Pillsbury during the dry season, leaving a marginal flow for fish, he said.

PG&E’s Moller said the summertime diversion takes water that was stored behind Scott Dam and wouldn’t otherwise be available. Mandated river flows downstream from the Cape Horn Dam are established to “mimic natural conditions” on the river, he said.

The Eel River watershed above Scott Dam covers 288 square miles, or about 7 percent of the river’s 3,971-square-mile watershed, the third largest entirely in California. Those headwaters could be a boon to spawning fish, if given access, restoration advocates say.

California Trout, a conservation nonprofit, is collaborating with Humboldt State University on an effort to determine how many spawning fish the upper Eel reaches could sustain, said Darren Mierau, the organization’s North Coast program director.

So far, the researchers have found 287 miles of habitat for salmon and steelhead, but CalTrout is still not calling for decommissioning of the Potter Valley Project.

Given the rampant damage to the Eel River from overfishing, logging, erosion and massive floods in 1955 and 1964, it’s difficult to assess the harm done by the dams, said Peter Moyle, a UC Davis biologist who has studied California freshwater fish for more than 40 years.

The river’s historic fish population, more than 1 million fish in good years, has declined by more than 99 percent, according to rough estimates, he said.

Removing Scott Dam “would be important for steelhead recovery but not essential,” he said in an email.

The steelhead count at Van Arsdale Reservoir behind the Cape Horn Dam is currently 57 fish, a “very low number,” marine fisheries biologist Fuller said. Gravel filled the fish ladder during the spawning run and probably curbed the count, which often reached the thousands in previous decades.

“We’re not seeing the population stability we’d like,” Fuller said, suggesting a target of 6,000 steelhead.

New threat and compromise

Biologists are also citing the latest threat to Eel fisheries — the proliferation of illegal marijuana gardens. A California Department of Fish and Wildlife study in 2015 estimated a total of nearly 90,000 pot plants growing throughout three Eel River tributary watersheds.

In some years, water demand by the thirsty plants could dry up some streams, stranding and killing fish, the study said.

Huffman and Mierau both suggested a way to maintain water diversions to Potter Valley and Lake Mendocino without dams, a so-called “run of the river” diversion during high water flows.

Pairing that with the long-awaited elevation of Lake Mendocino to increase its holding capacity might offer a “middle ground” to benefit fish and maintain water storage on the Russian River, Huffman said.

Davis, the Water Agency general manager, said the idea was worth considering, but Pauli said it wouldn’t work because the Army Corps of Engineers is required to release water from Lake Mendocino during the winter to maintain flood protection capacity.

Climate volatility — including the state’s protracted drought followed by the wettest winter on record — makes water supply management more difficult, Davis said.

“You can’t be wrong. You can’t make a mistake,” he said. “This is not the time to be risking reliable assets and questioning whether they are important to the community.”

But relicensing will most likely bring change, Huffman said.

“The status quo is unlikely to continue,” he said.

You can reach Staff Writer Guy Kovner at 707-521-5457 or guy.kovner@pressdemocrat.com. On Twitter @guykovner.